SelectLanguageForm::buildForm

public SelectLanguageForm::buildForm(array $form, FormStateInterface $form_state, $install_state = NULL)

public function buildForm(array $form, FormStateInterface $form_state, $install_state = NULL) {
  if (count($install_state['translations']) > 1) {
    $files = $install_state['translations'];
  }
  else {
    $files = array();
  }
  $standard_languages = LanguageManager::getStandardLanguageList();
  $select_options = array();
  $browser_options = array();

  $form['#title'] = 'Choose language';

  // Build a select list with language names in native language for the user
  // to choose from. And build a list of available languages for the browser
  // to select the language default from.
  // Select lists based on all standard languages.
  foreach ($standard_languages as $langcode => $language_names) {
    $select_options[$langcode] = $language_names[1];
    $browser_options[$langcode] = $langcode;
  }
  // Add languages based on language files in the translations directory.
  if (count($files)) {
    foreach ($files as $langcode => $uri) {
      $select_options[$langcode] = isset($standard_languages[$langcode]) ? $standard_languages[$langcode][1] : $langcode;
      $browser_options[$langcode] = $langcode;
    }
  }
  asort($select_options);
  $request = Request::createFromGlobals();
  $browser_langcode = UserAgent::getBestMatchingLangcode($request->server->get('HTTP_ACCEPT_LANGUAGE'), $browser_options);
  $form['langcode'] = array(
    '#type' => 'select',
    '#title' => 'Choose language',
    '#title_display' => 'invisible',
    '#options' => $select_options,
    // Use the browser detected language as default or English if nothing found.
    '#default_value' => !empty($browser_langcode) ? $browser_langcode : 'en',
  );
  $link_to_english = install_full_redirect_url(array('parameters' => array('langcode' => 'en')));
  $form['help'] = array(
    '#type' => 'item',
    // #markup is XSS admin filtered which ensures unsafe protocols will be
    // removed from the url.
    '#markup' => '<p>Translations will be downloaded from the <a href="http://localize.drupal.org">Drupal Translation website</a>. If you do not want this, select <a href="' . $link_to_english . '">English</a>.</p>',
    '#states' => array(
      'invisible' => array(
        'select[name="langcode"]' => array('value' => 'en'),
      ),
    ),
  );
  $form['actions'] = array('#type' => 'actions');
  $form['actions']['submit'] = array(
    '#type' => 'submit',
    '#value' => 'Save and continue',
    '#button_type' => 'primary',
  );
  return $form;
}